1. Introductory Information
This invention relates to a comprehensive, computer-based, medical method and apparatus for diagnosing and treating human disorders involving symptoms of dizziness, vertigo and imbalance. In particular, it relates to a unique and remarkably versatile system and methodology for examining, and where appropriate treating, and rehabilitating (reconditioning), the usual complex vestibular-system source of such symptoms.
As will be more fully elaborated below, vertigo, imbalance and related symptoms are often caused by, or related to, dysfunction in the central nervous system with regard to processing of visual, vestibular and somatosensory inputs. Thus, in some cases, and in relation to the utility of the present invention for rehabilitation, vestibular therapy, as performed by the invention, is directed toward retraining, reconditioning and habituating central nervous system processing in this regard. The methods of accomplishing this are many, but, as will be seen, may involve exercises that include isolating or denormalizing certain ones of the visual, vestibular and somatosensory inputs while exercising others. The present invention can readily carry out many of these exercises or tasks, under control of a computer, an operator, or the subject, or combinations thereof, via the control and processing structures and modalities offered and enabled by the invention. It can carry out exercises that consist of isolating or denormalizing certain of the visual, vestibular and somatosensory inputs, or others that encourage the coordination of these inputs. The system and methodology of the invention can prescribe the tasks, customize the character and complexity of the exercises to the subject, carry them out and document progress.
All of such examining, treating and/or rehabilitating activities are referred to herein as vertigo management. The system and method of the invention offer an opportunity to perform, in a unified setting, a very wide range of tasks relating to vestibular-system issues, including several novel tasks, such as real-time event-following correlation, not heretofore available.
2. Background Information
As was mentioned briefly above, the vestibular-system medical issues to which the present invention addresses its focus are complex. The background information which now follows generally outlines these issues, and sets the stage for a clear understanding about how the present invention deals elegantly with this complexity in a clearly intuitive versatile, flexible and straight-forward manner.
Dizziness, including vertigo and imbalance, is one of the most common complaints presented to the physician. Although these symptoms may be caused by a variety of abnormal conditions affecting either the peripheral or central nervous systems, the cause can most commonly be traced to abnormalities involving the vestibular endorgans in the inner ear or, less frequently, to their associated neural pathways in the brainstem or cerebellum. The vestibular endorgans are mechano-transducers that normally sense either angular or linear acceleration of the head. Thus, progress in diagnosing and treating the above disorders has been very dependent upon the ability to observe and quantify the reflex output of these vestibular sensors, and/or the subjective responses thereto.
The sensors of angular acceleration, which provide the percept of rotation in space in any plane, are the semicircular canals (also referred to as SC and SCC), which are located with three on each side within the inner ear, and oriented orthogonally to each other. Each semicircular canal acts as a transducer of rotation in the plane of its orientation. It contains fluid that, due to inertia, lags angular accelerations or decelerations of the head in the plane of the canal, and thereby actuates a sensor of fluid displacement, the cupula. This provides information via neural pathways to the brain stem that is carried via a reflex arc to the eye muscles, called the vestibulo-ocular reflex (VOR). During rotations of the head, this reflex keeps the eyes oriented in space via a counter-rotation until the eyeball reaches a certain point, whereupon there is a quick correction in the opposite direction called a saccade. When repetitive, this results in an involuntary jerking motion of the eyes called nystagmus that occurs in the plane of the semicircular canals that generate it. By observing this nystagmus under various conditions one can determine whether the semicircular canals are functioning normally and, if not, which canal is dysfunctional and the nature of the dysfunction. Also, the nystagmus can be followed in the course of treatment to monitor effectiveness. Dysfunction of the semicircular canals results mainly in symptoms of vertigo.
Quantitative assessment of the VOR under various conditions is carried out as a standard battery of tests known as nystagmography. When eye electrodes are used to detect eye movement, it is called electronystagmography (ENG). When video technology is used to detect eye movement, it is called videonystagmography (VNG). Testing is usually carried out in a light-obscuring environment in order to minimize the effects of optic fixation on the suppression of nystagmus. To varying degrees, nystagmus can also be suppressed by lack of alertness, certain drugs and habituation.
The standard ENG/VNG test battery includes a few standard head positions that are intended to provide an analysis of positional vertigo. Unfortunately, these test positions were standardized prior to the development of new knowledge regarding the causes of positional vertigo, such that they are not the ideal anatomical positions for obtaining useful information. For instance, certain key positions have been found where certain types of positional vertigo are aggravated and where the associated nystagmus is most easily detected, yet none of these is included in the standard test battery. Thus, new methods of investigating the causes of positional nystagmus and vertigo call for new standard positions for screening purposes, plus the triggering of more definitive tests when indicated, some of which require that the patient be maneuvered in ways that are most effectively practiced with a multi-axial positioning apparatus. In addition, nystagmus data is typically acquired and analyzed in small segments, completely ignoring the nystagmus occurring during intervening periods and transition moves. Inasmuch as the nystagmus occurring in a particular test position will be dependent upon numerous factors, such as the rapidity and method of the just-preceding transition maneuver, the time lapse after the test position is reached until the data-acquisition run is commenced, the exact angles of the test positions, etc., the usual ENG/VNG test battery as now generally carried out is not, in reality, standardized. Nor does it make optimum use of the data available.
The presence of many factors, some of which may be quite subtle, and of various time-changing and simultaneously interacting conditions, such as subject motions to, from and beyond various relevant spatial orientations, casts, the practice of vestibular-system investigation, treatment and rehabilitation with a need and desire for sophisticated real-time correlation, and succinct and cogent presentation of relevant unfolding facts and vestibular-system behaviors. In particular, it dictates for the need for thoughtful computer processing, and intuitive and quickly graspable situation presentation, preferably in clear visual (and especially pictorial) form, to aid the investigating/treating/rehabilitating physician, or other attending party. Subtle, nuanced responses to test, treatment and rehabilitation protocols, often interactively related to other simultaneous such responses, challenge accurate observability, and can easily escape significant notice, even to skilled observers whose attentions may be widely divided because of the attendant complexities of changing test parameters and subject responses. Such subtleties, however, will not escape the grasp of an appropriately employed computerxe2x80x94a grasp which can, and as will be explained below in accordance with the present invention, quickly and unfailingly furnish comprehensive presentations and analysis of interactive, correlative vestibular data.
What is needed, accordingly, is a method of carrying out the indicated screening and definitive tests, that can be automated and programmed to carry out and report intuitively on all tests and positionings in exactly the same manner and with the same timing each time employed.
Incidentally,where references are made herein to positions, positionings, orientations, and spatial orientations, those references are intended to involve either a subject""s static disposition in three-dimensional space, and/or a subject""s dynamic movement, in any direction or plane of motion, toward, through, and/or beyond one, or several, of such dispositions
Continuing with a general mention regarding where improvements and advances are welcome, it is also very desireable to implement tests and positionings, such as those outlined above, in a setting which is capable of interjecting certain more definitive tests when so indicated by the screening tests, that can perform examining approaches (tests) that are physiologically more meaningful and useful in diagnosing, treating and rehabilitating a subject, that can acquire data in a continuum throughout a procedure session, and that can, through careful programming, accomplish these tasks in as short a time as possible. Inasmuch as this can create a much larger volume of data than prior methods, structure and methodology must also be available that selects, analyzes and displays the data in a brief and understandable summary.
In the human vestibular system, the sensors of linear acceleration, the otolithic organs, called the utricle and saccule, are located on each side in the inner ear. Each is made up of a layer of heavy particles that is attached to hair cells that can, when stimulated, initiate a neural discharge. When the head is placed in various positions relative to gravity, or moves linearly in various directions, the resulting change in the inertio-gravitational vector acting upon the particles presents changing forces of strain that modulate the neural discharge of the attached hair cells. The resulting neural input leads to the brain stem, thence to the spinal nerves, and finally to the muscles of postural control in what is called the xe2x80x9cvestibulo-spinal reflexxe2x80x9d (VSR). Simultaneously, at a higher level, there is a subjective sense of the inertio-gravitational vector, called graviception, that in a normal subject is accurate to within a few degrees.
Abnormal conditions adversely affecting the otolithic organs cause mainly symptoms and signs of imbalance. This imbalance of otolithic origin results from either unstable neural input from an otolithic organ, or organs, or a bilateral deficit. Unstable neural input results from otolithic function that is either recently reduced from the normal, or is distorted from the normal input. This distorted neural input usually results from aberrant receptivity of the otolithic organ to non-gravitational forces such as sound and changing intralabyrinthine pressure. Central compensation generally takes place adequately over time for the reduced form if it is unilateral and becomes stable, but compensation is delayed or not forthcoming in response to the distorted form because of its persistent instability. Thus, the distorted form is by far the more common cause of chronic vertigo. It is seen frequently as the mechanism of post-traumatic vertigo.
My research has indicated that a quantifiable assessment of the distorted neural input arising as a consequence of aberrant receptivity of an otolithic organ can be accomplished in two ways: (1) by determining the adverse postural effects of either sound or changing intralabyrinthine pressure, as can be ascertained in the standing subject by observing, directly or by posturography, an increase in sway or a tendency to fall; and (2) by determining the adverse subjective effects of either sound or changing intralabyrinthine pressure on the directional perception of the inertio-gravitational vector. Such introduced sound and pressure stimuli perform what is referred to herein as denormalization of one or more of a subject""s perception capabilities. The problem with relying on adverse postural effects for this purpose, as by posturography, is that test subjects are usually acutely aware of their recent postural misperceptions that have resulted in abnormal sway or fall in a particular direction, and can quickly compensate for these misperceptions to some degree. Thus, if air pressure, or sound, that is presented to an ear canal of a standing subject with eyes closed were to cause a sway or fall in a particular direction, the next time the same stimulus is presented the subject will habitually tend to compensate by counteracting the sway or fall. This is because, on the first trial, the subject received somatosensory feedback from the feet and postural muscles indicating that involuntary sway or a fall, in a particular direction, took place. This tendency to compensate results in limited repeatability, and thus questionable reliability, of such a test using postural control as a measure. If, instead, both before (control) and during presentation of air pressure, or sound, to an ear canal, a test subject indicates his or her subjective perception of the gravity vector (graviception) by reorienting a visual object, and the subject cannot see the surround to obtain visual cues of the true gravitational vector, then the subject will not know if, or by how much, he or she deviated from the control in the subject-given indication of the gravity vector, and so cannot compensate for the deviation on the next trial. This novel graviception method results in greater repeatability and reliability, and its application in the present invention is discussed below.
In the practice of the present invention, the above mentioned xe2x80x9cvisual objectxe2x80x9d may be any image or physical object that provides a reference to gravity that can be presented to the subject combined with an input devicexe2x80x94button, lever, joystick, computer mouse, trackball, etc.xe2x80x94by way of which the subject responds to that image or object and thus introduces a subjective-response (voluntary) data-stream into a computer.
Many subjects with vertigo symptoms complain of aggravation of their symptoms by loud sound, or by conditions that are known to impart pressure change to the intralabyrinthine fluids. Aberrant receptivity of the labyrinth to sound or intralabyrinthine pressure change can occur in either the semicircular canals, thereby adversely impacting the VOR system and producing nystagmus, or the otolithic organs, thereby adversely impacting the VSR system and producing abnormal postural effects and altered gravitational perception. The latter condition, involving the VSR system, occurs far more frequently, yet standard testing of the effect of sound or intralabyrinthine pressure change involves only observation of the eyes. Thus, in the standard Hennebert (pressure) test and Tullio (sound) tests, the subject is seated, and the clinician only observes the eyes, either directly or with the assistance of magnification or electronic means, for abnormal nystagmus. Therefore, a method is needed for quantifying and localizing the effects of sound and intralabyrinthine pressure change on the VSR arc by monitoring their effects on postural control, or better yet, on gravitational perception.
The usual method (Halmagyi) of assessing a subject""s gravitational perception involves a seated subject in a light-proof enclosure who is given the task of repositioning a light-bar to the perceived visual vertical in the roll plane when the chair in which the subject is seated is tilted in the roll plane. This method has the disadvantage that no measurement is carried out in the pitch plane, although research indicates that distorted gravitational perception involves the pitch plane at least as much, and as often, as the roll plane.
In the present state-of-the-art, quantitative information on the status of both the VOR and the VSR requires two separate devices, taking up more space in the vestibular laboratory and adding to expense. In addition, several valuable existing tests that have not been utilized significantly outside of research laboratories because of the expense involved in the equipment to perform each test separately would ideally be integrated into one comprehensive system, and this consideration is very effectively addressed by the present invention.
Furthermore, state-of-the-art testing for position-evoked nystagmus is carried out largely in a few static positions, with conditions and convenience not allowing a more dynamic set of test maneuvers. In fact, the nystagmus patterns that subjects display in relation to introduced maneuvers are sometimes so complex that interpretation in real time is very difficult using present methods. Significant difficulty here arises, among other reasons, from the likelihood that the observing party""s attention is divided and scattered, rather than being condensed to enable clearer interpretation focus.
One example of this is seen with vestibular lithiasis, or benign paroxysmal positional vertigo and different variants, whereby abnormal particles in the semicircular canals render the canals sensitive to linear acceleration, including gravitation, creating symptoms of vertigo in response to a position change of the head relative to gravity. These conditions are very common, and can often be improved or corrected by repositioning maneuvers whereby the particles are moved, via sequential positioning of the subject""s head, and optional induced head oscillation, to an area of the labyrinth where they no longer produce abnormal responses. Most subjects with these conditions can be treated successfully by canalith repositioning maneuvers, including variations thereof collectively known as particle repositioning maneuvers. Such maneuvers are designed to cause migration of aberrant particles to an area of the labyrinth where they no longer affect the dynamics of the semicircular canals.
These maneuvers are typically carried out manually on a table with a high success rate in the less complicated cases. However, for the more complicated cases, optimal performance of these maneuvers requires ongoing and more challenging, real time observation and analysis of nystagmus. The nystagmus pattern may rapidly change during the performance of maneuvers, sometimes indicating the need for a critical change in strategy in the middle of the maneuver sequence. Present methods, whereby the subject is manually positioned on a table, have difficulty in accomplishing this. Further, the manual maneuvers for testing and treatment may introduce risk because of the abnormal bending and stretching of the neck and back that is required for their accomplishment. Such abnormal bending and stretching of the neck and back has been known to produce thrombosis of the neck vessels and strokes.
In addition, and as was mentioned above, nystagmus patterns that subjects may display in response to various maneuvers may be complex, and rapidly changing, and this may occur in situations where immediate interpretation is often required. Such a requirement usually becomes more acute when the need for a change in strategy is indicated (e.g. a conversion of the causative particles from the posterior to the horizontal canal, or the development of a jamming of the particles). In this kind of setting, there is a clear need for the operator, during the entire sequence of maneuvers, to envision the 3-D orientation with respect to space and gravity of the semicircular canals inside the head, and the apparent position of the particles within those canals. This is difficult, inter alia, because of the constant changing orientation in space of the subject during maneuvers, whether manual or automated. The operator task is even more deeply challenging in this regard where, in addition to the need for clear visualization of the real three-dimensional situation at hand, the operator needs to relate this situation quickly and effectively to the presentation of subject vestibular behavior, so as to advance an investigation, and/or to implement an appropriate treatment or rehabilitation maneuver.
Carrying out manual repositioning maneuvers on a table has many other limitations, such as difficulty moving heavy subjects, or those with back and neck problems. Also, it is often difficult to observe the nystagmus while physically maneuvering the subject. It is difficult to replicate exactly or to standardize manual maneuvers. Another limitation of a table for particle repositioning is that there is occasional need for a 360-degree maneuver, in either the yaw or the pitch plane of the head, while keeping the involved semicircular in a plane which contains the gravity vector. This is not feasible on a table or other standard equipment. Several devices have been devised for performing 360-degree maneuvers in these planes (Furman-Pittsburgh, Li), but none that can provide complete motion control in all planes, accompanied by constant monitoring, and including ease of interpretation of semicircular canal position and nystagmus throughout.
When maneuvering the subject for testing or treatment so that the head is in various positions, it becomes difficult to maintain an envisioned orientation of the relationship of the semicircular canals to gravity. Non-electronic devices placed on the head to assist the operator directly in perceiving the orientation of certain semicircular canals, as the head is moved into different head positions, have been used, and one such device has been demonstrated by Li, but these devices have definite limitations, such as physically interfering with the maneuvers, thereby creating errors in orientation due to varying anatomy of the head, and interference with viewing the nystagmus in certain positions.
Thus, for optimum positional testing and particle repositioning strategy, it would be very advantageous to have an automated system capable of positioning subjects through 360xc2x0 in all three degrees of angular freedom (pitch, roll and yaw), combined with a 3-D orientation and tracking system capable of simultaneously generating data regarding the actual orientation, relative to space and gravity, of the semicircular canals of the subject, as well as the angular acceleration being acutely imparted to the canals. Such data is preferably displayed to the operator in a form that projects pictorially the actual orientation of the semicircular canals within the subject""s head to a graphical user interface GUI image of the semicircular canals. Such an image would ideally reside in a simulated environment that makes the orientation of gravity evident, as well as makes evident the routes that are available, per mechanical positioning apparatus, for the next transition to another position. Further, for optimum and simplified control of the mechanical positioning apparatus, the directionality of the controls (right hand and left hand) for transition to other positions should be made obvious.
Although the ongoing spatial orientation of the subject""s head can be determined by sensors affixed to the positioning apparatus and by fixing the head thereto, it is often advantageous to fix an inertio-gravitational sensor, and/or a torque sensor, more directly to the head (such as fixed to the a head harness or to goggles). This avoids the necessity of fixing the subject""s head to the chair, such restraint being uncomfortable and anxiety-producing in some subjects. It also allows testing using the neck muscles to provide the torque necessary to reach high angular velocities of the head need for certain testing.
Although, in the state-of-the-art, sensors of spatial orientation have been fixed within a virtual reality headset in combination with miniature video screens, they have not been combined with video cameras, such as infrared-sensitive cameras, so that an observer can monitor ocular movement.
In this complex background setting, therefore, the present invention enters the scene with a remarkable and comprehensive capability to extract and acquire vestibular-related, medically informative data, and to present a simple, intuitive and clear picturing from such data of the abnormal behavioring of a very wide range of a human subject""s vestibular system.
As disclosed herein in its preferred form, the system of the present invention includes: (a) an appropriate spatial maneuvering device which can be employed, either manually (i.e., either by direct hand manipulation, or by manual adjustment of a hand-operable control device, such as a joystick), or under more automated computer control, to place a subject, and in particular the head of that subject, in many different orientations in space, thus to induce vestibular activity; (b) a digital computer (or computer processor); (c) display-screen structure in an image-display zone; (d) various transducers (sensor devices, or data-stream structures) for generating electronic data-streams (referred to herein as first-category and as second-category data streams) that are supplied to, and are processable by, appropriate control algorithm structure(s) in the computer processor; and (e) one or more video cameras which are employed to view various scenes during operation of the system, and to supply what is referred to herein as camera-derived information. Also included structurally, for different purposes, and in some instances optionally, are various devices (mentioned below) that are useful for doing what is referred to herein as denormalizing, changing and selectively controlling certain perception capabilities of a subject during diagnosis and/or treatment. Sound and pressure were earlier mentioned herein in relation to denormalization. Further included if desired, are one or more subject-useable control devices (the xe2x80x9cvisual objectxe2x80x9d mentioned above) which a subject can use, on request or command, to attempt to implement certain functions, and to provide certain subjective response data as will be described below.
With regard to the mentioned spatial maneuvering device for controlling a subject""s spatial orientation, this device could take on any suitable form, but for the purpose of describing herein a preferred embodiment of the invention, this device specifically takes the form of a chair which is appropriately mounted within a compound ring structure that is maneuverable angularly, and preferably under computer control, to position and move a subject""s head into substantially all possible planes of orientation. This chair device can thus be employed to introduce angular motion and acceleration to a subject.
With further regard to spatial maneuvering, linear movement and acceleration can also be important. For example, in testing the otolithic organs, it is sometimes desired to alter the inertio-gravitational vector relative to the subject without evoking an accompanying cue from the semicircular canals. One way of accomplishing this is to provide gross linear oscillation to the subject. This can be accomplished, as an illustration, with a linear track on which a subject-supporting chair unit travels on rollers or wheels to move the subject in a linear, oscillating manner. An important advantage of the present system for linear-oscillation testing is that a subject can be positioned through 360-degrees in any angle of the roll, yaw or pitch planes of the subject relative to the linear track and the direction of oscillation, thus providing a manner to test the otolithic organ through any plane of its functionality. State-of-the-art devices do not provide this capability. Combinations of other inputs described herein can be simultaneously applied during these linear oscillation tests, another capability not provided by state-of-the-art devices.
Other linear motion procedures may also be performed, and all such procedures can be practiced in accordance with the enhancement the capabilities of the present invention.
Thus, in broad terms, practice of the present invention in relation to investigation and diagnosis involves inducing vestibular activity in a subject by selectively orienting (positioning) that subject in different spatial dispositions, and by then collecting both absolute positional data (preferably from several sources, and referred to herein as first-category data relating to patterns and conditions of subject orientation), and subject-vestibular-response data relating to these dispositions (referred to herein as second-category data associated with patterns and conditions of a subject""s outwardly expressed behavior which is linked to vestibular activity). Such data is employed variously to generate (create) an easily viewed, pictorial, sophisticated visual correlation (or correlations) between certain components of the data, which correlation(s) play(s) an important role in informing the attending physician (or other party) about any problematic characteristics of the induced vestibular activity.
From the treatment and/or rehabilitation point of view, once a diagnosis has been achieved, the system computer, in a preferred manner of practicing the invention, can be instructed to execute one or a series of spatial-orientation maneuver(s) (linear and/or angular) to urge correction, etc. of the detected source problem. Manual maneuvering (by either of the xe2x80x9cmanualxe2x80x9d methods generally mentioned above) could also be employed on the basis of diagnostic information, especially as aided by guiding information given by, and as a result of, precision computer processing.